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-rw-r--r--src/algebra/boolean.spad.pamphlet35
1 files changed, 27 insertions, 8 deletions
diff --git a/src/algebra/boolean.spad.pamphlet b/src/algebra/boolean.spad.pamphlet
index 4fe76ef3..f0be1736 100644
--- a/src/algebra/boolean.spad.pamphlet
+++ b/src/algebra/boolean.spad.pamphlet
@@ -48,30 +48,49 @@ PropositionalFormula(T: PropositionalLogic): PropositionalLogic with
++ coerce(t) turns the term `t' into a propositional formula
coerce: Symbol -> %
++ coerce(t) turns the term `t' into a propositional variable.
--- variables: % -> Set Symbol
+ variables: % -> Set Symbol
++ variables(p) returns the set of propositional variables
++ appearing in the proposition `p'.
term?: % -> Boolean
+ ++ term? p returns true when `p' really is a term
term: % -> T
+ ++ term p extracts the term value from `p'; otherwise errors.
variable?: % -> Boolean
+ ++ variables? p returns true when `p' really is a variable.
variable: % -> Symbol
+ ++ variable p extracts the varible name from `p'; otherwise errors.
not?: % -> Boolean
+ ++ not? p is true when `p' is a logical negation
notOperand: % -> %
+ ++ notOperand returns the operand to the logical `not' operator;
+ ++ otherwise errors.
and?: % -> Boolean
+ ++ and? p is true when `p' is a logical conjunction.
andOperands: % -> Pair(%, %)
+ ++ andOperands p extracts the operands of the logical conjunction;
+ ++ otherwise errors.
or?: % -> Boolean
+ ++ or? p is true when `p' is a logical disjunction.
orOperands: % -> Pair(%,%)
+ ++ orOperands p extracts the operands to the logical disjunction;
+ ++ otherwise errors.
implies?: % -> Boolean
+ ++ implies? p is true when `p' is a logical implication.
impliesOperands: % -> Pair(%,%)
+ ++ impliesOperands p extracts the operands to the logical
+ ++ implication; otherwise errors.
equiv?: % -> Boolean
+ ++ equiv? p is true when `p' is a logical equivalence.
equivOperands: % -> Pair(%,%)
+ ++ equivOperands p extracts the operands to the logical equivalence;
+ ++ otherwise errors.
== add
FORMULA ==> Union(base: T, var: Symbol, unForm: %,
@@ -107,13 +126,13 @@ PropositionalFormula(T: PropositionalLogic): PropositionalLogic with
equiv(p,q) ==
binaryForm('equiv, p, q)
--- variables p ==
--- p' := rep p
--- p' case base => empty()$Set(Symbol)
--- p' case var => { p'.var }
--- p' case unForm => variables(p'.unForm)
--- p'' := p'.binForm
--- union(variables(p''.lhs), variables(p''.rhs))$Set(Symbol)
+ variables p ==
+ p' := rep p
+ p' case base => empty()$Set(Symbol)
+ p' case var => { p'.var }
+ p' case unForm => variables(p'.unForm)
+ p'' := p'.binForm
+ union(variables(p''.lhs), variables(p''.rhs))$Set(Symbol)
-- returns true if the proposition `p' is a formula of kind
-- indicated by `o'.